28728121 has 2 divisors, whose sum is σ = 28728122. Its totient is φ = 28728120.

The previous prime is 28728097. The next prime is 28728151. The reversal of 28728121 is 12182782.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28515600 + 212521 = 5340^2 + 461^2 .

It is a cyclic number.

It is not a de Polignac number, because 28728121 - 2¹⁵ = 28695353 is a prime.

It is not a weakly prime, because it can be changed into another prime (28728151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14364060 + 14364061.

It is an arithmetic number, because the mean of its divisors is an integer number (14364061).

Almost surely, 2^28728121 is an apocalyptic number.

It is an amenable number.

28728121 is a deficient number, since it is larger than the sum of its proper divisors (1).

28728121 is an equidigital number, since it uses as much as digits as its factorization.

28728121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3584, while the sum is 31.

The square root of 28728121 is about 5359.8620318064. The cubic root of 28728121 is about 306.2685533116.

The spelling of 28728121 in words is "twenty-eight million, seven hundred twenty-eight thousand, one hundred twenty-one".